UNGETC(3)

NAME
ungetc - un-get character from input stream

LIBRARY
libc

SYNOPSIS
#include <stdio.h>
int
ungetc(int c, FILE *stream);

DESCRIPTION
The ungetc() function pushes the character c (converted to an unsigned char) back onto the input stream pointed to by stream. The pushed-backed characters will be returned by subsequent reads on the stream (in reverse order). A successful intervening call, using the same stream, to one of the file positioning functions ( fseek(3), fsetpos(3), or rewind(3)) will discard the pushed back characters.

One character of push-back is guaranteed, but as long as there is sufficient memory, an effectively infinite amount of pushback is allowed.

If a character is successfully pushed-back, the end-of-file indicator for the stream is cleared.

RETURN VALUES
The ungetc() function returns the character pushed-back after the conversion, or EOF if the operation fails. If the value of the argument c character equals EOF, the operation will fail and the stream will remain unchanged.

SEE ALSO
fseek(3), getc(3), setvbuf(3)

STANDARDS
The ungetc() function conforms to ansiC and p1003.1-2001.

HISTORY
An ungetc() function appeared in AT&T UNIX.